Fix c/InternVariableWeakref.c.

The test was failing when building with gcc 4.8. It looks like weakrefs are
reachable via emit_varpool_aliases and emit_varpool_weakref. This causes us to
try to use rauw twice, causing an assert when we get a this->rauw(this).

The patch simply skips weakrefs in emit_varpool_aliases.

git-svn-id: https://llvm.org/svn/llvm-project/dragonegg/trunk@208010 91177308-0d34-0410-b5e6-96231b3b80d8